"I can tell you that it was a tip, a source from the public that initiated the initial investigation," said Nova Scotia RCMP Commanding Officer Brian Brennan. "We want people to know we became aware, we acted quickly and intercepted a threat."

He said a man and woman planned to go to a public venue in the Halifax region on Feb. 14 "with a goal of opening fire to kill citizens, and then themselves."

Brennan said a tip was received Thursday morning that a 19-year-old man from Timberlea and a 23-year-old woman from Geneva, Ill., had access to firearms and presented a significant weapons-related threat.

Police tracked the 19-year-old down to Tiger Maple Drive in Timberlea, entered the house and found him dead early Friday.The roles of the other male suspects, aged 20 and 17, of Halifax and Cole Harbour respectively, is still to be determined as part of the investigation, police said Friday night.

The Timberlea house is owned by Patricia Cody and John Gamble, according to a provincial government website.

At 2 a.m. Friday, police arrested the 20-year-old man and the female suspect at the Halifax Stanfield International Airport. The woman was arriving in Canada, and the man was meeting her.

"We believe we have apprehended all known individuals in this matter and eliminated the threat. We are not seeking any further suspects at this time in relation to this investigation," Brennan said.

"I wouldn't characterize it as a terrorist event. I would classify it as a group of individuals that had some beliefs and were willing to carry out violent acts against citizens."

He didn't say what the beliefs were, other than that "they were not culturally based."

The operation involved the Halifax police, RCMP, the Geneva Police Department in Illinois and other policing partners.

The Serious Incident Response Team is investigating the death of the man in Timberlea.

Police notified one specific venue of the threat, but would not say what venue that was.

"We are asking the public to remain vigilant about anything suspicious they may see or hear in their physical or online communities and to not hesitate to report anything to police," Brennan said at a news conference today.

'We always have to be vigilant'

Mike Savage, the mayor of Halifax, learned of the plot Thursday night when police briefed him.

"We have among the best emergency response in the country," he said. "The good news is they discovered all this and dealt with it very effectively. We always have to be vigilant."

Savage said he was taking police advice, but so far there are no plans to cancel any events Saturday.

Steven Blaney, the minister for public safety, commended the police effort.

"These arrests are a great example of the fine work they do on a daily basis to help keep Canadians safe. We support our law enforcement agencies who work tirelessly to ensure our communities are safe places to live, work and raise families," he said.

Corrections

An earlier version of this story said one of the three individuals detained had been released. In fact, as of midnight local time, three individuals were still in custody.